The present disclosure is directed to the improved process of dynamic bonding to create hybrid powder metallurgy parts.
Advanced aerospace designs continue to challenge materials and materials technology. While powder metallurgy materials offer unique advantages for many aerospace components, they could be further optimized if dissimilar materials could be bonded into a single component.
For example, in gas turbine engines, disks which support turbine blades rotate at high speeds in an elevated temperature environment. The separate portions of the disks are exposed to different operating conditions and temperatures. Thus, different combinations of mechanical properties are required at different locations. The high temperature rim portion has fatigue crack growth resistance and creep resistance, while the highly stressed hub portion has high burst strength at relatively moderate temperatures and fatigue crack growth resistance. The hub portion also has high resistance to low cycle fatigue for long component life.
Because of these differing requirements for the mechanical properties of the separate disk portions, and the extreme temperature gradients along the radius of a turbine disk, a single alloy is not well suited to satisfy the requirements of both the hub and the rim area of a modern turbine disk.
A possible solution is to use a dual alloy disk with different alloys used in the different portions of the disk, depending upon the properties desired. The disk has a joint region in which the different alloys are joined together to form an integral article.
Numerous techniques for fabricating dual alloy disks have been considered, such as fusion welding, inertia welding, diffusion bonding, bi-casting, and hot isostatic pressing which may be employed to consolidate powder used for one portion of a disk, such as the hub, and also to join it to the other portion. Many of these processes have drawbacks, for example, the disadvantage of hot isostatic pressing is that any impurities present at the joint prior to hot isostatic pressing will remain, and may be exacerbated by the lengthy time at elevated temperature and pressure.
Present powder-metallurgical techniques require three to four steps to produce a finished product. For example, producing tungsten requires pressing and pre-sintering, followed by a consolidation sinter and/or several hot-working steps. Dynamic bonding eliminates the need for large presses and expensive hot-pressing dies. In many instances, actual production time and costs may be reduced.